1. Field of the Invention
The present invention relates to a focusing device of a camera, more specifically to a focusing device of a camera that can easily adjust the focus of an optical unit of the camera such as a finder optical unit and a taking lens optical unit when assembling the optical unit.
2. Description of Related Art
Japanese Patent Application Laid-open No. 9-197491 discloses a finder optical system of a camera. In the optical system, lenses are held in lens frames, which are movably supported by a guide bar attached to a housing. A cam cylinder is arranged at a side of the lenses, and cam faces of the cam cylinder are engaged with the lens frames. The cam cylinder is rotated so that the lens frames can be moved back and forth along the cam faces so as to change a focal length of the optical system.
As a focusing structure of the finder optical system, a cam moving structure is applied. More specifically, the cam cylinder is moved back and forth with respect to the housing so that the entire lenses are moved back and forth, so as to adjust positions of the lenses along the optical axis and to thereby adjust the focus.
However, the conventional focusing structure requires many parts such as a pressing member for pressing the cam cylinder in a predetermined direction, and a moving member for moving back and forth the cam cylinder against the pressing force of the pressing member. Hence, the conventional focusing structure has a troublesome process to be assembled.
The present invention has been developed in view of the above-described circumstance, and has as its object the provision of the focusing device of a camera that can reduce the number of parts and be easily assembled.
In order to achieve the above-described object, the present invention is directed to a focusing device of a camera, comprising: a camera body; a cam member provided to the camera body; and a lens optical unit attached to the camera body, the lens optical unit including: a housing, a guide member provided by to the housing, a lens movable along the guide member, and an image forming part attached to the housing, wherein focus of the lens optical unit is adjusted by moving the housing with respect to the camera body in a state where the lens is engaged with the cam member.
According to the present invention, the lens optical unit is attached to the camera body and the lens of the lens optical unit is engaged with the cam member at the camera side. As moving the housing of the lens optical unit in this state, the position of the image forming part of the lens optical unit is adjusted while the lens is being fixed. Thus, the focus can be adjusted by only moving the housing. After the focusing, the housing is securely fixed to the camera body. Therefore, the focusing device of the present invention can be assembled without adding extra parts.
Moreover, if the focusing device of the present invention is applied to a finder optical unit and a taking lens optical unit, the focusing device for the finder optical unit and the photographing optical unit can be easily assembled.
Preferably, the guide member comprises a guide rod inserted through the housing, at least one of ends of the guide rod being supported by the camera body, the housing being guided by the guide rod when the housing is moved. In this structure, the housing is moved along the guide bar, which is also the guide member of the lens, and the housing is thus accurately moved along the optical axis of the lens. In a case where a plurality of lenses such as an objective lens and an eyepiece are attached to the housing in addition to the lens, the housing is moved in a state where the optical axes of the lenses correspond with each other; hence the optical accuracy is improved.